3. Mother Brain was always just above you

In the original Metroid game, the aim was to reach the game's final boss, Mother Brain. But what you didn't know was that its location was directly above you as you started the game. So near, and yet, so far.

4. Samus wasn't always going to be a lady

It turns out that one of gaming's biggest Easter Eggs wasn't always the plan. Initially Samus was a man.

"We were partway through the development process, when one of the staff members said 'Hey, wouldn't that be kind of cool if it turned out that this person inside the suit was a woman?'" explained game director Yoshio Sakamoto.

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5. Samus is the daughter of birds

According to the Metroid lore, Samus Aran was raised by birds.

The ancient, dying sentient bird people called the Chozo took her in and raised her as one of their own after the Space Pirate attack that killed her parents.

But instead of just raising her, they also trained her to fight so that they could bestow the signature Power Suit upon her.

6. Everything is the Chozos' fault

The Chozo may have created Samus Aran, but they also created the Metroids. The series' backstory reveals that the Chozo developed the bio-organisms in an attempt to clear the planet SR-388 of a different infectious species, the X parasites.

But the Metroids destroyed the X parasites and then turned against their masters, the Chozo.

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Unfortunately, the Chozo are also responsible for Mother Brain, but it, like the Metroids, turned evil.

7. Samus may have a living relative

In the interactive online story, Blood of the Chozo, made by Nintendo Power, it was revealed that Samus has a younger brother called Soloman Aran.

He's apparently "missing and presumed dead", which may well mean that he's still alive and ready for a spin-off.

8. She's always had a beauty spot

When Metroid: Other M arrived, fans were shocked and some outraged that Samus had a beauty spot near her chin.

Well, apparently, she's always had one.

When co-creator Yoshio Sakamoto was asked to reveal a secret about Samus that nobody else would know, do you know what he replied?

"I know where Samus' beauty mark is."

It only took 16 years for the game to get graphically detailed enough for us to actually see it.

9. The underwear Easter Egg doesn't exist in Japan

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To get the Easter Egg where Samus stands in all her ginger-haired glory and pink underwear, you either had to finish the game in under an hour or enter a special password.

The original Metroid was released as a Famicom Disc System game in Japan, however, which only had save slots to record your progress and no password system whatsoever.

The passwords only arrived when the game when to America in 1987, which came with the password functionality. And thus the "Justin Bailey" Samus was born (it was the most popular trigger password).

10. Justin Bailey doesn't mean anything

Because Justin Bailey was the most popular bikini trigger password, everyone thought it must have an ultimate meaning or be a reference to something.

Well, apparently it means absolutely nothing. It was just a random set of words, and there are a number of other phrases that trigger exactly the same effect. Sorry folks.

11. The morph ball is the result of animation struggles

The Morph Ball has always been one of Samus' signature moves but it was actually the result of the developers having a hard time creating a crawling animation.

Eventually Samus was given the ability to crawl in Metroid: Zero Mission, but this was a nod to the original struggles the studio had.

12. The discovery of the Morph Ball was intended as a puzzle

Samus' suit can be equipped with all kinds of crazy upgrades throughout the Metroid series, but the Morph Ball – or the Maru Mari – is the most famous.

It's been part of every Metroid game and there's even a spin-off dedicated to it – Metroid Prime Pinball, of course.

But the way you first discover the Maru Mari power up in the original game was designed to be a puzzle.

You found it by just heading left of the start position, which was a way to teach players they could scroll the screen left or right, which was quite the innovation in games at the time.

After all, you can only go right in Super Mario.

13. Animation issues weren't the developers' only struggles

The amount of memory space the developers had to work with for the original Metroid was extremely tight. That meant that no big changes could be made to the core engine, because it had to remain compatible with the Famicon – Metroid's original platform of choice.

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Therefore, to increase gameplay variety the ice beam was born.

It helped Samus navigate the world, changing enemies into stepping stones with a very simple change of colour, which took up very little memory on the disc.

14. The Varia Suit is a mistranslation

Although the name of Samus' suit is fairly iconic today, the Varia Suit isn't its original name.

Varia Suit is actually a mistranslation of Barrier Suit, named because it can withstand high temperatures and acid.

The developers decided to keep with the mistranslation because of the suit's "variable" nature.

15. And so was Planet Zebeth

In the first game, the opening story asks you to "defeat the metroid of the Planet Zebeth and destroy the mother brain, the mechanical life brain". But, that was actually a mistranslation of the Planet Zebes – the real name of the alien planet.

We'll let the Japanese developers off though, because the "s" and "th" sounds are interchangeable in Japanese.

16. The Metroids' home planet is named after a motorbike

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The home planet of the Metroids, SR388, is named after the SR400 Yamaga motorcycle engine series.

However, it's not called SR400 because although the engines in the bikes were called 400CC engines, they were only actually 388CC engines. And thus SR388 was born.

17. The enemies in Metroid are inspried by H.R. Giger

Although they're not actually designed by him, the enemies in the Metroid series are inspired by the surrealist creature artist H.R. Giger.

18. But its biggest inspiration is the movie Alien

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Many of you will know that the Metroid series' biggest inspiration is the Alien film franchise.

It uses the same science-fiction setting – a first for a Nintendo series – and Metroid also has a female lead, just like Sigourney Weaver's character, Ellen Ripley, in Alien. Then you've got the two characters both out to destroy a lethal alien menace that's threatening humanity.

Later on, it all gets even more connected as Ellen ends up bonding with the alien xenomorph species and Samus saves the baby Metroid at the end of Metroid II. The bond between Samus and the Metroid then becomes a major plot point in Super Metroid and Metroid: Other M.

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Samus eventually gets injected with Metroid DNA in Metroid Fusion in order to save her life, while Ellen gets cloned with xenomorph biology.

Of course, there's no forgetting that Samus' arch-nemesis is an endlessly reborn space dragon called Ripley, which was actually named after Alien director Ridley Scott.

19. Samus isn't designed to look like Sigourney Weaver though

Although the Metroid series is heavily influenced by the Alien movies, Samus' appearance is supposed to look like Kim Basinger, who Sakamoto watched in erotic drama 9 1/2 Weeks.

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20. The sounds of the bosses are something else altogether

So the art is Giger, the story is Scott, but what about the sounds? Well, the noises the bosses make in Super Metroid are actually sampled directly from various Godzilla movies.

Halfway through development, it was decided that the normal SNES noises weren't good enough and the team switched to sampling – a technique rarely used in games at the time.

21. Super Metroid was almost cancelled three times

Although the Metroid series is beloved across the world, it's never quite been able to match the success of the Mario or Legend of Zelda series, especially in its homeland Japan.

Because of this, Metroid co-creator Yoshio Sakamoto had to keep poking his bosses at Nintendo for nearly six months until he was granted to greenlight a SNES Metroid game in late 1991.

However, that didn't stop people like Game Boy creator and Metroid Producer from believing Super Metroid would be a total flop.

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"Yokoi-san was always angry when he saw us all completely absorbed and working crazy overtime on Super Metroid," explained Sakamoto. "He came in and said, 'Are you lot trying to produce a work of art or something?' Yokoi-san was becoming angrier with us day by day during that period."

Yokoi got so frustrated by the repeatedly delayed Super Metroid that he cut the game's budget and threatened to cancel it.

Thankfully, once the game was finished, Sakamoto revealed that Yokoi was "hooked" on Super Metroid.

22. And it was intended to be the last game in the series

Yoshio Sakamoto had originally intended to make Super Metroid the series' finale. That's basically why you had to wait eight years for another Metroid game.

However, in the early 2000s, Nintendo and American developer Retro Studios began work on the first person Metroid Prime.

In retaliation, Sakamoto made Metroid Fusion to make sure he still had a hand in the series he had created.

Of course, neither Metroid Fusion nor Metroid Prime were like the original games.

23. Super Metroid is amazingly tiny

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Super Metroid was the largest SNES game at the time it was created in terms of memory, clocking in at a 3MB. The biggest games eventually stretched to 16MB but that was still tiny compared to today's standards.

Put it this way, the smallest iPhone 6S size is 16GB and most AAA titles come in at around 40GB.

24. There are four secret moves hidden in Super Metroid

Even if you collected and mastered every upgrade in Super Metroid there were another four secret moves that you could only unlock by doing a very specific combination of moves.

You had to equip the Charge Beam and another beam, then select power bombs as your secondary weapon.

Start charging the Charge Beam, and then after a second or two, Samus will be briefly surrounded by swirling projectiles. The exact type will vary according to the secondary weapon you've got equipped – Ice, Wave, Spazer or Plasma Beam.

Et voila, a brand new weapon move.

25. And another way to refill your health without Energy Charge Stations

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Aside from those moves, there's another hidden ability in Super Metroid related to Samus' health.

Known as The Crystal Flash, this secret technique lets you regain the majority of your health without having to visit an Energy Charge Station.

However, it's extremely tricky to pull off. You have to have less than 50 energy, at least 10 missiles, 10 super missiles and 11 super bombs in your inventory.

If you've ticked all those boxes, you had to go into a Morph Ball, then hold down L, R and X to make Samus transform into a glowing orb that recharges most of her health.

26. There are three enemies that weren't even used

Hackers wading through Super Metroid's code discovered that within it lay three enemies that were totally unused in the game.

Bang – Similar to the Yameba from Metroid Fusion, the Bang was a large floating "cell" that increases in size when you shoot it. When they get large enough, they explode, and the more powerful your weapon, the more damage that explosion will deal to Samus.

Reflec – This security wall mount reflects shots when it's hit, meaning that shots can come back right at you. The idea was that you could use it to reflect means to hit otherwise protected switches.

Stoke – These cute little Crocomires were one of the first ones found in the game.

27. Metroid: Prime Hunters doesn't have any Metroids on it

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Despite the game's name, Metroid: Prime Hunters doesn't even have any Metroids in it – you know, the main enemy in the series.

What is odd though is that early demos of the game actually had Metroids in them, but they were removed by the time the game was released.

28. In Metroid: Other M, Samus' suit is powered by concentration

In Metroid: Other M, there are scenes were you can Samus' suit wavering in and out of existence.

It turns out that this is because Samus' suit is powered by concentration, and emotional stress causes Samus to lose grip on her suit.

"For Samus to remain connected with the Power Suit, it requires mental energy unfathomable to an ordinary person," exaplined Sakamoto back in 2004. "In situations like this when she is under pressure, indeed, even Samus is unable to concentrate her mental energy. However, when Samus completes the trial of the spirit of the mural (God of War), she regains her strong force of will and can successfully integrate with the Legendary Power Suit."

29. Metroid: Prime Hunters has the most timers in it

Racing against time to escape a self-destructing planet has been a staple in the Metroid series since the beginning. But no other title had quite so many timers in it as Metroid: Prime Hunters.

It's got the most countdown clocks in any Metroid game ever, keeping you permanently on your toes.

30. There was a Metroid N64 game in the pipeline

There was originally going to be a Metroid game for the N64, believe it or not. It was going to be called Metroid 64.

However, it was cancelled because the team couldn't come up with any "concrete ideas".

"I was actually thinking about the possibility of making a Metroid game for N64 but I felt that I shouldn't be the one making the game," said Yoshio Sakamoto. "When I held the N64 controller in my hands I just couldn't imagine how it could be used to move Samus around.

"So for me it was just too early to personally make a 3D Metroid at that time."